Currently, Low Dropout Regulators (LDOs for short), as power management circuits, have been widely used in fields such as portable electronic devices, wireless energy transmission systems, etc. The LDOs may be categorized into analog LDOs and digital LDOs according to characteristics of circuits. The analog LDOs have advantages such as a small output ripple, a high response speed etc., but due to their characteristics of analog circuits, their process migration performance is poor and their occupied chip area is large. In contrast, the digital LDOs have advantages such as good process migration performance and a small occupied chip area, and have disadvantages such as a large output ripple and a low response speed.